The present invention relates to irrigation systems and pertains particularly to an improved irrigation control diaphragm valve and screen.
The artificial distribution of water through irrigation systems is in wide use throughout the world today. One of the most widely used systems, particularly for lawn areas and playing or athletic fields, is the sprinkler system wherein a plurality of sprinkler units are positioned about a land area for distributing water over the surface of the land area. One or more control valves control the distribution of water to the sprinkler units within the system.
Commercial, industrial, municipal and golf course irrigation systems increasingly rely on alternative water sources including reclaimed water as an irrigation water source. This trend has been prompted by an often critical need to conserve water in most regions of the country. Other alternative water sources include lakes, reservoirs, wells, and the like. However, since water from these sources is often relatively dirty, its use has brought with it an increase in the incidence of clogging of various components of irrigation systems. While the obvious solution is simply to filter the water entering the irrigation system, the cost of such filters, and their maintenance, limits the degree of filtering that is economically feasible.
The problem of clogging in irrigation systems is most acute in areas in the system where water must pass through small openings. Such systems having small openings occur, for example, in irrigation systems having pressure responsive control valves, pressure regulating valves, in drip systems, and in other low flow irrigation configurations.
For example, in irrigation systems having pressure responsive and pressure regulating valves, have a main diaphragm valve that is normally pilot operated with upstream or inlet water pressure which passes via a small passage to the back of the main diaphragm valve to apply valve closing pressure. In pressure regulating valves the down stream water pressure, which is directed to the sprinklers, is regulated by a feedback mechanism. The main diaphragm valve normally pilot operated with upstream or inlet water pressure fed via a small passage to the back of the diaphragm to maintain it closed. The passage is normally from the face or front of the valve to the back thereof. A grit screen is placed at the inlet of the passage to screen out small particles that may clog the passage.
One widely used prior art screen is illustrated in FIGS. 1 and 2 and comprises a retaining washer on the end of the diaphragm shaft having ribs which standoff against a stainless steel washer on the face of the valve. Water passes through grooves formed between the ribs and washer to a restricted spiral passage in a friction plate to a control chamber behind the valve. This construction is complicated and expensive to make because of the many parts required.
Referring to FIG. 1, there is illustrated an exemplary prior art pressure regulating valve of a type commonly used in irrigation systems. This pressure regulating valve is a diaphragm-type valve which includes an inlet port 12 for receiving irrigation water and an outlet port 14 for conveying water to one or more sprinkler stations. The pressure regulating valve 10 controls the flow of water from the inlet port 12 to the outlet port 14 by means of a diaphragm valve assembly 16 which is raised or lowered from a valve seat 18 to turn the valve on and off. As illustrated in FIG. 1, the valve is in the OFF position, since a diaphragm seal 20 is in contact with the valve seat 18.
The diaphragm assembly 16 includes a diaphragm 44 in the form of an annular resilient member which permits reciprocal up and down motion of the diaphragm assembly 16. The pressure regulating valve 10 also includes a solenoid 24 which is operable by means of an electrical signal to actuate a solenoid valve 26 to move between raised and lowered positions. Above diaphragm 22, there is a diaphragm pressure chamber 28 into which water from the inlet port 12 flows through a metered pathway to be described. A diaphragm chamber outlet pathway 30 permits water to flow from the diaphragm chamber past the solenoid piston 26 and, when the solenoid is in the upward, or open, position, to a crossover pathway 32. Crossover pathway 32 is also connected to an outlet pathway 34 which permits water to flow to the outlet port 14.
In operation, when the solenoid piston 26 is in the down position, no water is allowed to flow out of the diaphragm chamber 28 through the diaphragm outlet pathway 30. As a result, pressure in the diaphragm chamber 28 builds up to equal the pressure in the inlet port 12. However, the area above the diaphragm, which is affected by the pressure in the diaphragm chamber, is greater than the area below the diaphragm seal 20, which is affected by the pressure in the inlet port. As a consequence, there is a resultant downward force on the diaphragm valve assembly 16 which causes it to close the diaphragm seal 20 on the valve seat 18. The valve 10 is then in the OFF position and no water can flow from the inlet port 12 to the outlet port 14.
When the solenoid 24 is energized by a signal from an irrigation controller (not shown) carried on an electrical wire 36, the solenoid operated valve 26 moves up. This permits water to flow out of the diaphragm chamber 28 and then to the outlet port 14 by way of the diaphragm outlet pathway 30, crossover pathway 32 and outlet pathway 34. As a result, pressure in the diaphragm chamber 28 will decrease enough so that the pressure at the inlet port 12 is higher by an amount sufficient to raise the diaphragm valve assembly off the valve seat 18. This allows water to flow from the inlet port past valve seat 18 and directly into the outlet port 14.
The diaphragm valve assembly 16, as seen in FIG. 1, comprises an annular diaphragm 44 having a peripheral rim 46 which is secured in post-annular grooves between the upper and lower housings of the valve assembly. The diaphragm has an inner peripheral rim 48 which is clamped between a friction plate 50 having upstanding walls which are engaged by a retaining insert 52 for clamping the inner peripheral rim 48 of the diaphragm. A diaphragm seal member 20 is clamped in a recess in the friction plate 50 by means of a retaining plate or screen 56. The retaining plate or screen 56 is held in position by a diaphragm shaft 58 which extends upward into a bore in an adjusting assembly in the center of the valve body. A retaining washer 60 on the inside phase of the friction plate 50 retains the shaft 58 in place. The retaining plate or screen 56 is formed with radially extending ribs or grooves that form radially extending water passages between the ribs or within the grooves as it engages against a stainless steel washer 62, engaging the front or upstream face of the diaphragm seal member 20.
Water for pressurized operation of the diaphragm valve is metered or screened through the passages formed by the grooves at the engagement of the screen 56 and stainless steel washer 62 and passes into an annular radially spiraling groove 64 in the phase of friction plate 50 forming a restricted passage way which exits at 66 into the diaphragm chamber 28 behind the diaphragm 44. The pressure exerted by the water in diaphragm 28 controls the pressurized sealing of the diaphragm seal 20. As shown in FIG. 1, a screen and retaining washer have a throughbore for receiving a diaphragm shaft, a stainless steel washer, a valve seal, a friction plate, a retainer washer and a retainer insert to secure the assembly to an annular diaphragm.
Accordingly, there is a need for simpler more effective and inexpensive diaphragm valve with a simpler more effective screen.